1. Field of the Invention
The present invention relates generally to magnetic disk drive lubrication systems.
2. Description of the Related Art
Certain types of hard disk drives can include a lubricant reservoir packet that provides lubrication to the heads and disks within the hard disk drive continuously over the useful life of the hard disk drive. Typically, the geometry of the reservoir packet is a thin rectangular structure that is comprised of synthetic and/or natural fibers or a suitable foam or sponge-like medium contained in a particle-free woven fabric covering or other particle-free medium. The selected media must allow for containment of the lubricant and permit suitable airflow. The reservoir packet contains a specified quantity of volatile lubricant that is held therein by capillary interaction with the aforementioned fibers. Vapor from this lubricant source communicates with all of the heads and disks within the disk drive. The reservoir packet stores a specific volume of lubricant that is transferred to the heads and disks in order to keep them constantly lubricated so as to prevent premature failure of the disk drive.
Ordinarily, the reservoir packet includes a quantity of lubricant sufficient to last the entire lifetime of the disk drive. Unfortunately, in certain cases it is possible for the reservoir packet to prematurely run out of lubricant possibly resulting in premature failure of the drive. This may occur if the disk drive does not remain adequately sealed thereby resulting in excessive leakage of lubricant vapor from the disk drive enclosure. It may also be useful to assess field performance by monitoring reservoir quantity as a function of time and operational environment.
The present invention accordingly recognizes that there currently is a need for monitoring the lubricant in the reservoir packet and alerting the user when the reservoir packet is almost empty in order to allow the user the chance to backup the files contained in the disk drive before failure of the drive. In the case of extreme depletion, an option allows the drive to be turned off to prevent imminent failure preceding backup.
A disk drive includes at least one head, at least one disk and a lubricant reservoir packet that contains or incorporates an electrical transducer capable of monitoring the amount of lubricant remaining therein. The remaining lubricant is in vaporous communication with the head and disk. The disk drive also includes a controller that uses the transducer to measure an electrical characteristic associated with the lubricant reservoir packet and generates a signal when the remaining lubricant in the reservoir packet is nearly exhausted. The transducer may use a physical characteristic of the lubricant for the purpose of assessing the remaining amount. Suitable characteristics include the lubricant""s dielectric constant, electrical conductivity, viscosity, surface tension, migration in an imposed electrical field, physical mass, or by other means.
In one embodiment, the electrical transducer can either be placed within the reservoir packet or close to the packet so as to sample only a small representative portion of the packet. Conversely, in an alternative embodiment, the transducer can encompass all or a substantial portion of the reservoir packet. An example of the first embodiment is a small crystal oscillator fitted with a narrow thin-film strip (micro-thread), all of which is surface-treated. The strip is physically intertwined with the fibers comprising the reservoir packet so that it communicates liquid lubricant via capillary flow with the oscillator to indicate the lubricant quantity remaining in the reservoir packet. Similarly, a micro device sensitive to either viscosity or surface tension can provide an assessment of the remaining liquid lubricant in the aforementioned reservoir packet. An example of the second case includes two parallel, electrically conductive plates placed on either side of the reservoir packet. The plates are designed and positioned to have a fixed, substantial contact with the reservoir packet and an electrically conductive lubricant thus allows the quantity of lubricant to be assessed via electrical conductivity (resistivity). Because most lubricants have a high dielectric constant, the quantity of lubricant can also be assessed by a similar arrangement of parallel plates by monitoring the capacitance of the system. To allow a pathway for molecules of the lubricant to vaporize from the reservoir packet into the drive""s enclosure, one or more of the referenced parallel plates may contain a suitable array of small holes such that the physical measurement is not substantially affected. On the other hand, the plate(s) may be substituted by a suitable electrically conductive screen.
In a preferred embodiment, the electrical characteristic measured by the controller is the electrical capacitance of the lubricant reservoir packet after it is fitted with conductive plates. Preferably, the plates are established by first and second metal screens, and a reservoir packet containing a metered amount of lubricant is disposed between the screens which establishes a characteristic capacitance. The screens can be designed so as to allow airflow through the reservoir packet. As lubricant is consumed, the capacitance of the packet declines. Also in a preferred embodiment, the controller is connected to an output device that receives a signal when the lubricant reservoir packet is nearly empty of lubricant.
In another aspect of the present invention, a method for monitoring lubricant within a disk drive includes providing a lubricant reservoir packet and disposing a lubricant reservoir transducer proximal to the reservoir packet. Using the transducer, an electrical characteristic of the lubricant reservoir packet is measured.
In yet another aspect of the present invention, a method for monitoring lubricant within a disk drive includes measuring an electrical characteristic of a lubricant reservoir packet when it is empty and also after it has been filled with a metered quantity of lubricant thereby establishing the full range of the electrical characteristics. Then, it is determined when the electrical characteristic falls below a predetermined percentage of the initial value of the electric characteristic. When the electrical characteristic falls below the predetermined percentage of the initial value, a warning signal is generated. The drive can be automatically shut down if the user does not take action within a certain period of time after the warning signal is generated, or after the electrical characteristic indicates that a more critical depletion of the lubricant reservoir has occurred.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: